The present invention relates to a sewing machine frame made from a synthetic resin in which an arm portion, a tower portion and a bed portion are provided integrally. The present invention also relates to a sewing machine having the sewing machine frame.
In the sewing machine frame, a horizontally extending arm portion supports a reciprocation mechanism for a needle carrying a needle thread, and the tower portion vertically extends from the bed portion for supporting the arm portion in a cantilevered fashion. In the bed portion, a loop taker is supported for trapping a loop of the needle thread carried on the vertically reciprocating needle in order to form a stitch.
In the sewing machine, a smooth stitching operation is required. To this effect, vibration and displacement of a needle tip due to the vertically reciprocating motion of the needle must be reduced or minimized, otherwise a loop seizing beak of the loop taker disposed in the bed portion cannot trap the needle thread loop formed by vertical reciprocation of the sewing needle. Thus, the stitching may be degraded.
In order to avoid this problem, the needle and rotary hook timing must be adequately provided. To this effect, the sewing machine frame must provide high rigidity capable of avoiding deformation or displacement thereof due to reaction force occurring when the needle penetrates a workpiece fabric. Therefore, in the conventional sewing machine, a metallic frame having high rigidity is provided in an interior of a sewing machine cover, and a stitch forming mechanism including a needle vertical reciprocating mechanism and the loop taker is attached to the metallic frame.
However, such a conventional arrangement is costly, bulky and heavy. More specifically, the sewing machine frame has a rigid box shape arrangement in order to provide high rigidity. Further, the frame is made from a metal such as a cast iron or aluminum, which in turn increase weight and size. Further, high skill and elaboration is required for assembling the sewing machine because the stitch forming mechanism must be installed into the metallic frame through a small area opening thereof. This increases assembly cost.
Laid open Japanese Patent Application Kokai No. Hei-11-137880 discloses a sewing machine frame made from a synthetic resin to reduce production cost and to provide a light weight frame. As shown in FIG. 16, the frame 300 has an open end arrangement in a U-shape cross-section in which a bed portion 304, a tower portion 303 and an arm portion 302 are provided integrally, and a reinforcing plate 301 is fixed between upper and lower portions at the open end of the bed portion 304.
However, the disclosed sewing machine frame 300 provides a rigidity still lesser than that of the metallic frame. More specifically, as shown in FIG. 16, vertical vibration occurs in the arm portion 302 due to a load exerted along a vertical line containing the needle, the load being caused by the reciprocating motion of the needle during stitching operation. Further, a horizontal swing also occurs at an upper portion of the tower portion 303 during stitching.
Such vibration and swing occur due to the cantilevered support structure of the arm portion 302 with respect to the tower 303. That is, a combination of the arm portion 303, the tower portion 303 and the bed portion 304 provides an arcuate recessed wall 305, and a stress generated by the vertically reciprocating motion of the needle will be concentrated on the wall 305. However, the wall 305 does not have a sufficient rigidity, and therefore, such unwanted vibration and swing occur to lower stitching quality in comparison with the conventional sewing machine provided with the metallic frame.
It is an object of the present invention to overcome the above-described problems and to provide a sewing machine frame having a bed portion, a tower portion and an arm portion those integrally with each other and formed of a synthetic resin, yet having high rigidity, and to provide a sewing machine having such an improved sewing machine frame.
This and other objects of the present invention will be attained by a sewing machine frame for use in a sewing machine including a frame member, and a peripheral wall reinforcing rib. The frame member is formed of a synthetic resin and has a bed portion, a tower portion upstanding from the bed portion, and an arm portion extending from the tower portion at a position above the bed portion. The bed portion, the tower portion and the arm portion are formed integrally and provide a concaved peripheral wall defining a stitch working space. The peripheral wall reinforcing rib protrudes from the frame member. The peripheral wall reinforcing rib extends along the peripheral wall and ranges at least from a boundary between the bed portion and the tower portion to a boundary between the tower portion and the arm portion.
In another aspect of the invention, there is provided a sewing machine frame for use in a sewing machine including an outer panel wall, a side wall, a peripheral wall reinforcing rib, and an outer panel wall reinforcing rib. The outer panel wall constitutes a front wall and a rear wall and has a peripheral edge. The side wall protrudes from the peripheral edge to provide a closed space with the outer panel wall and is formed integrally with the outer panel wall with a synthetic resin. A combination of the outer panel wall and the side wall provides a bed portion, a tower portion upstanding from the bed portion, and an arm portion extending from the tower portion and positioned above the bed portion. The side wall has a part providing a concaved peripheral wall which defines a stitch working space surrounded by the bed portion, the tower portion and the arm portion. The peripheral wall reinforcing rib protrudes from the outer panel wall and extends along the peripheral wall. The peripheral wall reinforcing rib ranges at least from a boundary between the bed portion and the tower portion to a boundary between the tower portion and the arm portion. The outer panel wall reinforcing rib protrudes from the outer panel wall for reinforcing the same.
In still another aspect of the invention, there is provided a sewing machine frame including a bed portion, a tower portion upstanding from the bed portion, and an arm portion extending from the tower portion in a cantilevered fashion, a stitch forming mechanism of the sewing machine being assembled in the sewing machine frame. The sewing machine frame includes an integral main frame body, an integral frame cover and a concave wall reinforcing rib. The integral main frame body is made from a synthetic resin and to which the stitch forming mechanism is assembled. The integral main frame body includes a back panel wall having a first peripheral edge, and a first side wall integrally protruding from the first peripheral edge. The integral main frame body provides an arm section, a tower section and a bed section. The integral frame cover is made from a synthetic resin and is attached to the main frame body. The integral frame cover includes a front panel wall having a second peripheral edge, and a second side wall integrally protruding from the second peripheral edge for providing a complementary bed section to form the bed portion with the bed section, a complementary tower section to form the tower portion with the bed section, and a complementary arm section to form the arm portion with the arm section. The first side wall and the second side wall have parts defining a concave wall surroundingly provided by the combination of the arm portion, the tower portion, and the bed portion. The concave wall reinforcing rib extends along the concave wall and ranges at least from a boundary between the bed portion and the tower portion to a boundary between the tower portion and the arm portion.
In still another aspect of the invention, there is provided a sewing machine frame for use in a sewing machine including an outer panel wall, a side wall, and a reinforcing member. The outer panel wall constitutes a front wall and a rear wall. The side wall protrudes from a peripheral edge of the outer panel wall to provide a closed space with the outer panel wall and is formed integrally with the outer panel wall with a synthetic resin. A combination of the outer panel wall and the side wall provides a bed portion extending in its longitudinal direction, a tower portion upstanding from the bed portion, and an arm portion extending in its longitudinal direction from the tower portion and positioned above the bed portion. A congregated area among the bed portion, the tower portion and the arm portion provides a concaved peripheral wall defining a stitch working space of the sewing machine. The reinforcing member is formed integrally with the outer panel wall and has a generally semi-circular hollow cross-section. The reinforcing member is positioned along the peripheral wall and has one end portion positioned in the arm portion and extending in the longitudinal direction thereof, and has another end portion positioned in the bed portion and extending in the longitudinal direction thereof.
In still another aspect of the invention, there is provided a sewing machine frame including a bed portion, a tower portion upstanding from the bed portion, and an arm portion extending from the tower portion in a cantilevered fashion, a stitch forming mechanism of a sewing machine being assembled in the sewing machine frame. The sewing machine frame includes an integral main frame body, an integral frame cover, and a reinforcing member. The integral main frame body is made from a synthetic resin and to which the stitch forming mechanism is assembled. The integral main frame body includes a back panel wall having a peripheral edge, and a side wall integrally protruding from the peripheral edge. The integral main frame body provides an arm section, a tower section and a bed section. The side wall has a part defining a peripheral wall surroundingly provided by the combination of the arm section, the tower section and the bed section. The integral frame cover serves as a front panel wall and is made from a synthetic resin and is attached to the main frame body for providing a complementary bed section to form the bed portion with the bed section, a complementary tower section to form the tower portion with the tower section, and a complementary arm section to form the arm portion with the arm section. The reinforcing member is formed integrally with the main frame body and has a generally semi-circular hollow cross-section. The reinforcing member is positioned along the peripheral wall and has one end portion positioned in the arm section and extending in the longitudinal direction thereof, and has another end portion positioned in the bed section and extending in the longitudinal direction thereof.
In still another aspect of the invention, there is provided a sewing machine including a stitch forming mechanism and any one of the above-described sewing machine frames.